Spinal cord injury (SCI) results in detrimental effects on the upper and lower urinary tract. Currently there is no effective therapy for urological dysfunction. Having control over voiding function is of primary importance to this patient population as this affects independence, overall health, and self-image. Current attempts at treatments with various drugs and surgeries have unwanted side effects and limited success. One of our goals is to provide a natural therapeutic alternative. Body weight supported treadmill training is advancing our knowledge on how the spinal cord can learn and adapt, and the results of its positive effects for SCI patients continues to grow. We have clinical observations from patients that step training can have beneficial outcomes on bladder maintenance and that there is an inhibitory interaction between the limbs and the bladder. Therefore, we propose to study these observations in a clinically relevant animal model to identify mechanisms involved. Eighty-six male rats will receive a 225 kdyn force contusion injury at the T8 spinal level using the IH impact or device. Twenty-six rats will be implanted with a bladder catheter and EMG wires in the soleus and tibialis anterior muscles to determine the influence of noxious and innocuous bladder afferent input on locomotor (vesico-somatic) performance in intact, SCI, and inflammatory conditions. The role of C-fiber inputs will also be determined via capsaicin pre-treatment. Inflammation and distention from bladder may be altering sensory inputs for the lumbosacral cord, in turn altering the ability for locomotor output and spinal learning. Beginning 14 days post-injury, twenty rats will undergo daily step training on a treadmill with manual assistance for 8 weeks. Two other groups forelimb trained (n=20) and non-trained (n=20) will be tested simultaneously. Functional urological data will be obtained with 1) conscious cystometry- catheter infused saline and 2) natural voiding patterns gathered using a metabolic monitoring system. Terminal molecular studies eleven weeks post- SCI will assess the exercise's regulation of bladder mRNA content of various neurotrophic factors, which have been identified as important modulators in both the exercise and bladder dysfunction literature. Thus, this study will be the first to investigate the influence of exercise therapy on the spinally mediated reflexive relationship between viscera and somatic structures involving detrusor, external urethral sphincter, and limb musculature. Although partially masked in normal subjects, these reflexes are highly apparent after an upper motor neuron disease or SCI. Each part of this study is specifically designed to be applicable to the SCI patient and activity based therapies such as locomotor training. PUBLIC HEALTH RELEVANCE: Both quadriplegics and paraplegics rank bladder function as one of the most important factors affecting their quality of life, and 96.5% of 681 survey respondents believe that exercise is an important part of functional recovery yet at least 63.6% do not have access to a trained therapist to oversee their regiments. With over 1 million people in the U.S. alone affected by SCI and the annual cost in federal funds estimated at $9.7 billion, the knowledge gained from our study on locomotor training effects on bladder function will not only be immediately applicable to patients, providing immense improvements in quality of life, but also reduce life-long burdens on patient, family, and care centers.